Three-dimensional dynamic geometry of the normal canine mitral annulus and papillary muscles.

BACKGROUND

Despite an incomplete knowledge of the geometry and dynamics of the mitral annulus (MA), papillary muscle (PM), and the chordae tendineac, chordal-sparing MVR is popular.

METHODS AND RESULTS

The systolic reduction in three-dimensional distance between each PM tip and eight MA sites (DT-A) was measured in nine normal closed-chest dogs by use of surgically implanted radiopaque markers. Three loci (tip, junction, and base) on each PM were also projected onto the MA plane at end diastole and end systole to assess PM dynamics. The anterior PM tip showed significant shortening of DT-A toward the opposite side of the MA or the midanterior MA region (P < .005 or P < .05, respectively, versus same MA side [MANOVA]); conversely, the posterior PM tip DT-A shortened toward the opposite side of the MA near the anterior commissure or the area between the anterior commissure and midposterior MA (P < .005 versus same MA side). Annular projection revealed three-dimensional motion (relative to the MA) of the anterior PM tip, junction, and base toward the right trigone, while posterior PM motion was oriented toward the opposite side of the MA.

CONCLUSIONS

Both PMs in normal canine hearts demonstrated systolic relative motion in a direction compatible with the "oblique" chordal configuration, ie, from the anterior PM to the anterior MA near the right trigone and from the posterior PM to the opposite side of the posterior MA. These observations warrant further investigation of three-dimensional PM-MA dynamics with various methods of chorda preservation during MVR to assess their impact on left ventricular systolic and diastolic function.